title: Increased post-operative ischemia in the femoral head found by microdialysis by the posterior surgical approach: a randomized clinical trial comparing surgical approaches in hip resurfacing arthroplasty.
abstract: BACKGROUND
  Hip resurfacing arthroplasty (HRA) is associated with osteonecrosis of the femoral head and femoral neck fracture, which may be caused by a decrease in the perfusion of the bone initiated at surgery. Several studies have demonstrated a decreased blood flow during surgery depending on the choice of surgical approach. We investigated the effect of the surgical approach on the blood flow and metabolism in the femoral head and neck in HRA by Laser Doppler flowmetry (LDF) and microdialysis.
  
  
  METHODS
  We conducted a randomized clinical trial on 38 patients, allocated to HRA by either the posterior (Post) or the antero-lateral (AntLat) surgical approach. LDF was performed during surgery and microdialysis after surgery to assess the concentration of the following metabolic markers: glucose, lactate, pyruvate and glycerol.
  
  
  RESULTS
  At 44-50 h after surgery, the mean lactate/pyruvate (L/P) and lactate/glucose (L/G) ratio was higher in the Post group compared to the AntLat group; L/P 195.3 (SEM 123) in Post and 128.5 (108.0) in AntLat; L/G 16.9 (6.5) in Post and 8.9 (3.7) in AntLat (p L/P = 0.02 and p L/G = 0.03). There was no difference in the LDF measurements (p = 0.74).
  
  
  CONCLUSIONS
  HRA in the posterior approach results in increased post-operative ischemia in the femoral head and neck although during surgery, no difference in the blood flow was found. Still, the antero-lateral approach also causes considerable ischemia and other possible explanations, such as damage to the retinacular vessels during surgery or altered microcirculation because of heating from the cementation process, needs to be investigated.
authors.affiliation: Orthopaedic Research Unit, Aarhus University Hospital, Tage-Hansens Gade 2, Building 10A, Office # 33, 8000, Aarhus C, Denmark, nina.dyrberg.lorenzen@ki.au.dk.
authors.forename: Nina Dyrberg
authors.initials: ND
authors.lastname: Lorenzen
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
authors.forename: Michael
authors.initials: M
authors.lastname: Ulrich-Vinther
authors.forename: Niels
authors.initials: N
authors.lastname: Trolle-Andersen
authors.forename: Thomas
authors.initials: T
authors.lastname: Prynø
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Hanne
authors.initials: H
authors.lastname: Birke-Sørensen
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D005260:Female; D005270:Femur Head / Q000098:blood supply* / Q000601:surgery; D005272:Femur Neck / Q000098:blood supply* / Q000601:surgery; D006801:Humans; D007511:Ischemia / Q000175:diagnosis* / Q000209:etiology; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D012212:Rheology